package migrate

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"io/fs"

	"code.icb4dc0.de/prskr/searcherside/core/ports"

	"ariga.io/atlas/sql/migrate"
	"ariga.io/atlas/sql/postgres"
	"ariga.io/atlas/sql/sqlite"
)

var _ ports.Migrator = (*AtlasMigrator)(nil)

type AtlasMigrator struct {
	MigrationsFS fs.FS
	RevisionRW   ports.RevisionReadWriter
}

func (a AtlasMigrator) Migrate(ctx context.Context, req ports.MigrationRequest) (err error) {
	dialectFS, err := fs.Sub(a.MigrationsFS, req.Driver.String())
	if err != nil {
		return fmt.Errorf("no migrations sub-directory found for dialect %s: %w", req.Driver, err)
	}

	migrateDriver, conn, err := migrationDriverFor(req.Driver, req.URL)
	if err != nil {
		return err
	}

	defer func() {
		err = errors.Join(err, conn.Close())
	}()

	executor, err := migrate.NewExecutor(migrateDriver, readOnlyFSDir{FS: dialectFS}, a.RevisionRW)
	if err != nil {
		return err
	}

	pendingFiles, err := executor.Pending(ctx)
	if err != nil {
		return err
	}

	for idx := range pendingFiles {
		if err = executor.Execute(ctx, pendingFiles[idx]); err != nil {
			return err
		}
	}

	return nil
}

func migrationDriverFor(driverName ports.Driver, url string) (drv migrate.Driver, db *sql.DB, err error) {
	conn, err := sql.Open(driverName.String(), url)
	if err != nil {
		return nil, nil, err
	}

	defer func() {
		if err != nil {
			err = errors.Join(err, conn.Close())
		}
	}()

	switch driverName {
	case ports.DriverSQLite:
		drv, err = sqlite.Open(conn)
		return drv, conn, err
	case ports.DriverPostgres:
		drv, err = postgres.Open(conn)
		return drv, conn, err
	default:
		return nil, nil, fmt.Errorf("unknown driver: %s", driverName)
	}
}